Onions are a versatile vegetable that can be grown in gardens big and small. Their pungent flavor adds depth and complexity to many savory dishes. Onions are also known for their pest-repelling properties, making them a valuable addition to any edible garden. But what should you plant alongside your onions to maximize their growth and flavor? Here is a comprehensive guide to the best and worst companion plants for onions.
Why Onion Companion Planting Matters
It’s hard to smell other plants around onions and other alliums like garlic and leeks because their smell is so strong. This makes it harder for bugs like cabbage worms and carrot flies to find the plants they want to eat. If you plant onions next to vegetables, herbs, and flowers, you can keep pests away without using pesticides.
In addition to pest control, certain plants actually boost the growth and flavor of onions when planted nearby through symbiotic relationships. Other plants compete with onions for nutrients and space or inhibit their growth through allelopathic chemicals. Knowing the companion plants that have positive, negative or neutral effects on onions is key to a successful garden.
The Best Companion Plants for Onions
Many common fruits, vegetables, herbs and flowers make excellent onion companion plants. Here are some of the top options:
Vegetables
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Onions: Onions hide onions from onion flies, and carrots hide from carrot flies. Their roots are at different depths in the ground, so they don’t compete for nutrients.
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Beets: Beets thrive in the same conditions as onions. Onions may help protect beets from fungal diseases.
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Lettuce: Fast-growing lettuce can be interplanted with onions to maximize space. The onions deter pests from the lettuce.
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Tomatoes: Onions make tomatoes taste better and keep aphids, asparagus beetles, and other pests away that eat tomatoes.
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Potatoes: Onions drive away potato beetles, aphids and other major pests. Both prefer looser, well-draining soil.
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Spinach: Onions mask the scent of spinach, protecting it from insects and rabbits.
Herbs
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Dill: Dill improves the growth and flavor of onions. The onions’ scent masks the dill from pests.
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Parsley: Parsley deters carrot flies, allowing onions to grow pest-free.
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Chamomile This herb boosts onion growth and flavor
Flowers
- Marigolds: Marigolds suppress nematodes and other soil-dwelling pests that attack onion roots. Their bright blooms also repel deer.
Plants to Avoid Growing Near Onions
Some plants cut down on onion growth or compete with them for soil resources. Keep these plants away from your onion plants.
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Beans: Beans and onions stunt each other’s growth.
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Peas: Peas and onions should not be interplanted.
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Asparagus: Onions stunt asparagus growth and alter the flavor.
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Garlic and shallots: Separate onion relatives to prevent diseases from spreading between them.
General Onion Companion Planting Guidelines
Follow these tips for the healthiest, most productive onion beds:
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Rotate all alliums to different beds each year to prevent disease buildup.
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Plant quick-maturing lettuce between slower growing onions. Harvest the lettuce once the onions need more space.
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Group onions, carrots, beets and other root crops together for crop rotation purposes since they feed heavily.
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Use taller companion plants like tomatoes or pole beans to shade smaller onion plants.
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Include dynamic accumulators like comfrey, yarrow or dandelions to bring nutrients to the surface for shallow-rooted onions.
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Plant onions on the sunny side of larger companion plants to protect them from harsh sunlight in summer.
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Add marigolds, nasturtiums or other pest-repelling flowers to make an onion-friendly border around veggie beds.
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Use onions as a protective barrier plant along the edges of plots susceptible to rabbits, deer and other wildlife.
Best Companion Planting Combinations with Onions
Some of the very best companions for onions include:
Onions + Carrots
This classic pairing helps mask the scent of each vegetable from pests. Both thrive in loose, fertile soil. Sprinkle onion sets between carrot rows or alternate rows of each.
Onions + Tomatoes
Onions drive away aphids, slugs, asparagus beetles and other pests that plague tomatoes. The tomatoes provide shade for onion bulbs.
Onions + Beets
With similar soil needs, beets and onions make ideal bedfellows. Onions may help reduce fungal leaf spot on beets.
Onions + Lettuce
Plant lettuce between onion rows or vice versa. The onions deter rabbits, insects and diseases from the lettuce.
Onions + Brassicas
Onions help repel cabbage worms, aphids, Japanese beetles and other pests that damage broccoli, Brussels sprouts, kale and other brassicas.
Onions + Strawberries
The strong onion scent disguises strawberries from aphids, slugs, snails and other threats.
The Takeaway
Thoughtful companion planting with onions can increase yields, improve pest control and boost flavor in your garden. Use this guide to identify beneficial neighbors to plant near your onions as well as crops that should be kept far apart. Pay attention to sun requirements, harvest times and growth habits when designing your onion companion planting scheme. With the right plant partners, your onions will thrive!
Benefits of Companion Planting
Native Americans often used companion planting to balance soil nutrients and environmental support that corn, bean, and squash plants require.
By planting these crops in close proximity, they could share or replenish the nutrients the other crops needed while also creating a hospitable habitat for growth. The corn provided a trellis for the beans, the beans replenished the nitrogen in the soil, and the squash leaves provided shade to maintain moisture and reduce weeds.
This shows how planting three different kinds of plants in the same garden could be good for all of them and make it easier for plants to grow. Adding other plants can also increase crop productivity and control pests. Onions are a great example of a plant that excels at pest control. Using a plant to help control insects is an environmentally friendly method that can be used as an alternative to using pesticides or other synthetic chemicals.
Before you plant a herb or vegetable garden, check your list of plants to see which ones don’t get along and which ones should be next to each other. Then, plan your garden accordingly. The benefits will be worth the little bit of extra planning.
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Onion companion planting – with vegetables (Image credit: Leigh Clapp)
There is a wide range of vegetable crops that are perfect partners for onion companion planting. If you practice onion companion planting alongside crop rotation you will increase your chances of a healthy harvest.
CARROTS
Planting onions, specifically growing spring onions, with carrots is a classic combination that many gardeners swear by. The smell of onions deters carrot root fly from the carrots for carrot companion planting, while the smell of the carrots helps to deter onion fly from the onions – a highly beneficial pairing.
However, there have been mixed reports of the success of this method, with some gardeners convinced, while others are less sure.
If you are really worried about carrot fly, you can stretch Enviromesh or fleece three feet high around the edges of the carrot bed. The pest is a ground flyer and won’t make it over the screen, advises gardening expert Sarah Raven.
CABBAGE
Onions get on well will all members of the cabbage family (brassicas), which also includes lettuce and broccoli. This is because companion planting with onions provides good resistance to cabbage worm, weevils and cabbage looper. The aroma of the onions also helps to confuse rabbits seeking out the scent of leafy greens to enjoy.
TOMATOES
Due to their strong scent, onions also deter aphids and Japanese beetles from running amuck over your tomato plants, so are ideal for tomato companion planting, and tomatoes will not compete with onions for soil nutrients.
PEPPER
Plant onions around the base of your peppers to deter aphids and Japanese beetles.
Planting Onion Sets: What to Watch Out For
FAQ
What should not be planted next to onions?
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Growfullyhttps://growfully.comBest (and Worst) Onion Companion Plants – GrowfullyApr 23, 2022 — What should I NOT plant with onions? Onions are mostly friendly with everyone in the garden, with a few notable examples. Do not plant onions with:
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The Sprucehttps://www.thespruce.com18 Onion Companion Plants to Grow – The SpruceApr 8, 2025 — Onions should not be planted with peas, beans, asparagus, or sage. … Onions make great companion plants for many fruits, vegetables, herbs, and flo…
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MasterClasshttps://www.masterclass.comHow to Grow Onions: Onion Companion Planting Guide – 2025Jun 7, 2021 — 11 Companion Plants to Grow With Onions. Onions make great planting companions due to their ability to improve the flavor of their companion plants,
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Homes and Gardenshttps://www.homesandgardens.comOnion companion planting: the best crops to grow with onionsJul 11, 2022 — What vegetables should not be planted with onions? There are various vegetables that you should not plant with onions. You should not grow peas, bea…
What plant does not like onions?
Some plants do not get along well with onions. These include beans and peas, as well as cabbages. The essential oils that onion plants spread do not benefit the growth of cabbage. In addition, you should not grow plants with similar root growth to onions in their vicinity.
Can peppers be planted with onions?
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Pest control:Onions’ strong aroma repels many common garden pests that can also target pepper plants.
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Space efficiency:Onions don’t take up much vertical space, allowing peppers to grow tall without competition.
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No nutrient competition:Onions and peppers don’t generally compete for the same nutrients, according to the Spruce.
What grows well with onion sets?
Any crop in the cabbage family, such as broccoli, cabbages, cauliflower, kale, collards, mustard, and kohlrabi is beneficial to onions. These plants will keep unwanted pests away from onions and help enhance flavor, says Langelo.